(x-3)2 - 3(x-3)-28

Question

the 2 after first set of parentheses is squared

Answer 1

Let's let t = (x - 3). 

Our problem then looks like t² - 3t - 28, which factors to (t - 7)(t + 4)

Replacing t with (x - 3), we get
[(x-3) - 7][(x-3) + 4]  or

(x - 10)(x + 1)

We could also brute force it:
(x² - 6x + 9) - 3(x - 3) - 28

x² - 6x + 9 - 3x + 9 - 28.

Now, collecting like terms,
x² - 9x -10

(x - 10) (x + 1)